Install it with go get:

go get -u github.com/AlekSi/gocoverutil

gocoverutil contains two commands: merge and test.

Merge command merges several go coverage profiles into a single file. Run gocoverutil merge -h for usage information. Example:

gocoverutil -coverprofile=cover.out merge internal/test/package1/package1.out internal/test/package2/package2.out

Test command runs go test -cover with correct flags and merges profiles. Packages list is passed as arguments; they may contain ... patterns. The list is expanded, sorted and duplicates and ignored packages are removed. go test -coverpkg flag is set automatically to the same list. Only a single package is passed at once to go test, so it always acts as if -p 1 is passed. If tests are failing, gocoverutil exits with a correct exit code. Run gocoverutil test -h for usage information. Example:

gocoverutil -coverprofile=cover.out test -v -covermode=count github.com/AlekSi/gocoverutil/internal/test/...